Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$41.65	3.356%	$43.0478	$43.05	$43.05	$43.00
Purchase #2	$84.95	5.336%	$89.4829	$89.48	$89.50	$89.50
Purchase #3	$70.32	6.406%	$74.8247	$74.82	$74.80	$74.80
Purchase #4	$135.33	12.634%	$152.4276	$152.43	$152.45	$152.40
Purchase #5	$240.40	11.311%	$267.5916	$267.59	$267.60	$267.60
Purchase #6	$63.94	11.448%	$71.2599	$71.26	$71.25	$71.30
Purchase #7	$198.85	9.380%	$217.5021	$217.50	$217.50	$217.50
7 purchase totals =	$835.44		$916.1366	$916.13	$916.15	$916.10